Presented by:

Sharon Shaji

CONTENTSINTRODUCTION

OCCURRENCE OF GYPSUM

PRODUCTION

CALCINATION

GYPSUM PLASTERS

GYPSUM BOARD

PROPERTIES AND USES

OTHER USES

UNIQUE PROPERTIES

GYPSUM THROUGH THE AGES

MARKET SURVEY

REFFERENCES

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INTRODUCTION Gypsum is a rock like mineral commonly found in the earth’s crust, extracted, processed and used by Man in construction or decoration in the form of plaster and alabaster.

During the time of the Pharaohs, Gypsum was used as

mortar in the construction of the Cheops Pyramid (3000 B.C.).

Chemically it is CaSo4.2H2O i.e. Calcium Sulphate Dihydrate.

Impurities: MgO, Al2O3, Fe2O3, SiO2, CaCO3, MgCO3.

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• Colour- transparent to whiteand can be of grey, green ,pink, blue and

red because of impurities

OCCURRENCE OF GYPSUM

A common mineral, with thick and extensive evaporite beds in association with sedimentary rocks.

Gypsum is deposited in lake and sea water.

Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near surface exposures.

Often associated with the minerals halite and sulfur.

PRODUCTION STEPS

Excavating

Crushing (~25 mm diameter)

Grinding

Heating (calcining)

Cooling and Pulverizing

Marketing in Bags

CALCINATION

Gypsum rock when heated to 100-190°C looses ¾ of its water.

CaSO4.2H2O → CaSO4.½H2O + 3/2 H2O

Plaster of Paris

This is low burning process and named as INCOMPLETE

CALCINATION.

When calcination is carried out at temperatures above 190°C all water is removed.

CaSO4.2H2O → CaSO4 + 2H2O

gypsum anhydrite

This is high-burning process & COMPLETE CALCINATION.

Both of these products form gypsum rock by recombining with water.

CaSO4.½H2O + 3/2H2O → CaSO4.2H2OCaSO4 + 2H2O → CaSO4.2H2O

Calcination process is carried out in two types of kilns.Kettle KilnsRotary Kilns

KETTLE KILN

HEAT

FIRE BRICK

~ 2.5-3 cm

~ 2-3 m

DISCHARGE

GYPSUM ROCK

MIXER

ROTARY KILN

GYPSUM PLASTERS Obtained by Incomplete Calcination (CaSO4.½H2O)

1. Plaster of Paris : is formed by incomplete calcination at 100-190°C. No admixtures are found.

2. Hard Wall PlasterPlaster of Paris + Admixtures (Glue, Sand...)

Obtained by Complete Calcination (CaSO4)

1. Flooring Plaster (CaSO4 with no impurities)

2. Hard Finish Plaster (CaSO4 + Al2(SO4)3)

(CaSO4 + Na2B4O7)

What is Gypsum Board?

Gypsum board, commonly known as drywall, is the technical product name used by manufacturers for a specific board with a gypsum core and a paper facing.Gypsum board is the premier building material for wall, ceiling, and partition systems in residential, institutional, and commercial structures and is designed to provide a monolithic surface when joints and fastener heads are covered with a joint treatment system.

Making Gypsum Board

•To produce gypsum board, calcined gypsum is mixed with water and additives to form a slurry which is fed between continuous layers of paper on a board machine. •As the board moves down a conveyer line, the calcium sulfaterecrystallizes or rehydrates, reverting to its original rock state. •The paper becomes chemically and mechanically bonded to thecore.•The board is then cut to length and conveyed through dryers toremove any free moisture.•Gypsum manufacturers also rely increasingly on “synthetic”gypsum as an effective alternative to naturalgypsum ore.

PROPERTIES AND USES OF GYPSUM PLASTERS

Plaster of Paris•Setting time ~5-20 min.•Used for sculpturing, ornamental work, small repair works.

Hard Wall Plaster•Setting time ~1 hr•Compressive strength ~7 MPa•Admixtures result in increased plasticity & setting time & reduced shrinkage•Can be used for plastering walls•Production of prefabricated structural units•Masonry bricks & blocks

Flooring, Hard Finish Plaster•Setting time ~1-16 hrs•Compressive strength > 7 MPa•Can be used for producing prefabricated units, masonry bricks & blocks & flooring & pavement bricks & tiles.

Gypsum often serves as a fire proofing material even though its strength is destroyed by long continuous heat. It forms a powder covering the surface which acts as an effective insulator.

Gypsum products tend to disintegrate when exposed to moisture. Therefore, they should not be used for exterior work & for moist interiors.

(NON-HYDRAULIC)

OTHER USES OF GYPSUMGypsum can indeed also:

Be added to some bread and dough mixes as a Calcium source and baking aid.

Be used as a filler and fire retardant in plastic products.

Be used in Portland cement and special cement products for set and expansion control.

Be a source of Calcium and Sulphate Sulphur for plant growth.

Be used as a modelling material for tooth restorations.

Be an ingredient in many patching compounds.

Be used with glass to fabricate large, lightweight architectural decorations.

Be used as a mould material to fabricate custom body parts for trucks and automobiles.

Be an aid in juice extraction of some fruits and vegetables

The Modern Use of Gypsum in Construction: Plasterboard

The modern use of Gypsum as a building material was discovered in 1888 when the American Augustine Sackett invented a machine for producing plasterboards (also known as wallboards and dry walls) composed of several layers of paper with

Gypsum in-between.

In Eastern and

Western Europe,

there are currently

more than 200 factories

producing plasterboards.

Uses of Gypsum Products in

Home Interiors Plasterboards• Plasterboard is used for partitions and the liningof walls, ceilings, roofs and floors. The propertiesof plasterboard can be modified to meet specific requirements, such as fire resistance, humidity resistance, impact resistance, etc.

Decorative Plaster• Plaster powder, mixed with water, manually or through the use of silo-supplied spray systems, isused to create an effective and aesthetically-pleasing lining for brick and block walls, and for ceilings. • Gypsum’s adaptability in application lends itself to moulding and shaping. Since time immemorial, Gypsum has been used by skilled craftsmen to create decorative plaster mouldings.

Building plaster• Gypsum plaster is used for walls and ceilings.

Plaster blocks• Gypsum blocks are used for partitions and Gypsum tiles for ceilings.

Gypsum based self levelling screeds• Anhydrite or Alpha- Hemihydrates are used in the production of self levelling floor screeds.

Gypsum Fibreboards•Gypsum fibreboard is used for partitions and lining of walls, ceilings, roofs and floors. Gypsum Fibreboard offers good performance when it comes to impact resistance, sound insulation and humidity resistance.

Gypsum Products Unique

Properties1) FIRE PROPERTIES

•Due to the natural composition of Gypsum, gypsum plasterboards are inherently fire resistant. •The chemical formulation of Gypsum is CaSO4.2H2O - Calcium Sulphate Dihydrate.•In nature, Gypsum occurs in the form of crystals.•The presence of water in Gypsum (H2O), one square meter of plasterboard of 15 mm thickness contains around 3 litres crystal water. •Through the action of fire, the crystal water evaporates and a protective layer of Gypsum is formed. •Behind this layer, the material under fire attack, remains at constant temperature around 100oC as long as water is released from the Gypsum.

• The inclusion of glass fibres in Gypsum boards enhances their fire protection performance by maintaining the integrity of the board in a fire.

•Gypsum is a powerful fire retardant element in the construction sector due to its non-combustibility and ability to delay for up to 4 hours - according to the number of plasterboards in the corresponding system - the progression of fire.

2) ACOUSTIC PROPERTIES

•The Gypsum Industry has a beneficial impact on noise reduction as it produces special acoustic grade plasterboard which offers greater sound extinction which can be applied where a particularly high performance is required.

•Drywall systems provide effective sound insulation because they are designed to provide a physical barrier to sound, incorporate a sound break and minimise reverberation. •Between the two sides of the partition there is an air cavity, which interrupts the flow of sound.

•Because the two sides of the partition are separate it is harder for impact sound to pass through.

•These characteristics mean that a typical drywall partition in a house can be only 75mm thick. A comparable masonry wall would need to be 110mm thick to achieve the same sound performance.

3) THERMAL PROPERTIES

•Lightweight building techniques (plasterboard on framework) can supply excellent thermal performance since the construction has a cavity that can be filled with the required amount of insulation.

•The interior plasterboards protect the insulating material and contribute, together with the vapour barrier, in preventing indoor humidity from getting in, or being trapped in, the insulation material.

• Gypsum equilibrates humidity and heat peaks

•Gypsum is capable of storing humidity when a room is humid and automatically releasing this humidity if the indoor air becomes too dry.

•Plasterboards have also a “heat-storing” ability. Small temperature increases are absorbed and radiated back later when the temperature in the room decreases.

4) AESTHETICS AND DESIGN

•A richness of forms can be created in plasterboard or stucco. •For architects, building with gypsum products allows them to unleash their creativity thus allowing them to answer, even more dramatically, to the demands of their customer while remaining within an affordable budget. •In short, Gypsum allows the creation of stunning interiors in any and all styles, from the Classical to the Modern.

5) EASE OF ISTALLATION

•One of the principal reasons for this rapidly growing popularity is ease of installation. •To construct an internal wall, for example, a frame is erected, plasterboard is fitted to it, joints are filled, and the wall is created. •The operation is clean, dry and uncomplicated. •A gypsum finish can also be applied to the surface of the plasterboard in order to achieve a superior finished appearance.

Gypsum Through the Ages

•As demonstrated by its presence in the Egyptian

pyramids, gypsum has served as a vital piece of many

famous construction projects throughout history.

•Over thousands of years, this important mineral has

demonstrated its versatility and sturdiness and has

become a staple in today’s homes, buildings and

structures.

•This section provides an informative look at what gypsum

is, the history of its use and how gypsum board is made.

Ancient EgyptCenturies of Reliability

Gypsum has been used in construction since the days of ancient Egypt, where it was used in building the Pyramids. Some of this construction is still visible over 5,000 years later, a tribute to gypsum’s durability as a building material.

•Alabaster is a form of gypsum used both in building and as a decorative material. •Large deposits of gypsum were discovered near Paris, and “Plaster of Paris” became a popular building material. •Plaster of Paris is raw gypsum that is chemically altered by heat to remove much of the water naturally occurring in gypsum.•French farmers also used natural gypsum as a soil additive to improve crop yields.

19th centuryGypsum Boards in Construction

The use of gypsum boards in construction began in the late 19th century, after Augustine Sackett patented “Sackett Board,” layers of thin plaster of Paris placed between wool felt paper.

•Sackett Board was often used as a replacement for wood and as a base for the application of plaster. In 1893, the exterior of the World’s Columbian Exposition palace in Chicago was finished with gypsum plaster bound with fibre.•By 1916, Sackett’s product was a ready-to-finish board for use in construction, similar in concept to today’s modern gypsum board.

20th CenturyThe Gypsum Industry Booms

The demands for rapid construction of military housing brought about by World War I led to a sharp increase in the demand for gypsum board. After a barracks fire tragically took the lives of several servicemen, gypsum board’s fire-resistant qualities made it the preferred choice in military housing.

•Because gypsum offered significant advantages over traditional heavy masonry and concrete, the gypsum industry focused on expanding its use in commercial construction. •To meet the demands of high-rise building, theindustry developed gypsum board

shaft wall systems and movable partitions systems as well as improved fire resistance. •The tallest buildings in the world at that time—the John Hancock Tower, at 100 stories,and the Sears Tower, at 110 stories—used gypsum board in construction.

JOHN HANCOCK TOWER

SEARS TOWER

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Modern DayThe Gypsum Industry Today

Now, with over 97% of new homes using gypsum board, it is clearly the interior construction material of choice.

As a result of gypsum’s remarkable ability to adapt, to be recast and reformulated into many different and valuable materials, the industry continues to innovate while meeting today’s demands for environmental stewardship.

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• THE COMPANIES THAT MARKET GYPSUM PRODUCTS ARE: AEROSTONE, VANS GYPSUM, SAINT GOBAIN GYPROC, INFINITE IMPEX, ETC.• GYPSUM IN MARKET IS AVAILABLE IN BOARD FROMS OR SQUARE TILE FORMS• THE AVERAGE GUARANTEE GIVEN TO THESE PRODUCTS IS NEARLY 30 YRS.

TYPE RANGE SIZE IN MM PRICE INR/TILE

PRICEINR/BOX

GRG TILES REGULAR 595 X 595 X 7 99.62 796.94

MEDIUM 595 X 595 X 15 156.21 937.27

HIGH 595 X 595 X 29 382.38 1147.43

TYPE RANGE SIZE IN MM PRICE INR/ SFT

PRICE INR/BOARD

GYP BOARD REGULAR 1830 X 1220 X 9

16.82 403.62

HIGH 1830 X 1220 X 12.5

20.64 495.30

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REFERENCES1) http://www.eurogypsum.org/_Uploads/dbsAttachedFiles/

livingwithgypsum.pdf

2) http://www.gypsum.org/about/gypsum-101/history-gypsum/

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